jiangsu & ece, page-4

Tanzania is Africa's second largest economy? What about Nigeria?
http://en.wikipedia.org/wiki/Nigeria

Nigeria, known as "the Giant of Africa", is the most populous country in Africa and the seventh most populous country in the world.[10] Its oil reserves have brought great revenues to the country. Nigeria is considered to be an Emerging market nation by the World Bank.[11] Nigeria's economy is the second largest in Africa, and the 37th largest in the world as of currently.[12] Nigeria has been identified as a regional power, it also has regional hegemony, and major influence within its region.[13][14][15] It is listed among the "Next Eleven" economies. Nigeria is expected to become the largest economy in Africa overtaking South Africa in the near future and become one of the world's Top 20 economies by 2050.[13]

Nigeria is a member of both the Commonwealth of Nations, and the African Union.